(Sen) - Scientists using data from NASA's Kepler space telescope have revealed details of a rocky 'super Earth' planet and a gas giant akin to Neptune orbiting closely together around a star named Kepler-36. The two planets are closer together than in any other planetary system so far discovered.
Kepler-36 is approximately 1,200 light years away and about 2 billion years older than the Sun. Orbiting the star are Kepler-36b and Kepler-36c.
The inner planet, Kepler-36b, is a rocky planet 1.5 times larger than Earth and estimated to weigh 4.5 times our home planet. It orbits its parent star every 13.8 days at an average distance of less than 11 million miles. This inner rocky planet is believed to be made of 30% iron.
The outer planet, Kepler-36c, is a gas giant planet about 3.7 times larger than Earth. It orbits its star every 16.2 days at an average distance of about 12 million miles. Its mass is eight times that of Earth. Kepler-36c is essentially a "hot Neptune" having the properties similar to Neptune but orbiting much closer to its star. Unlike the inner smaller planet, Kepler-36c is primarily made of hydrogen and helium, with perhaps an inner rocky core.
At their closest Kepler-36b and Kepler-36c come within 1.2 million miles of each other - about 5 Earth-Moon distances.
Within our Solar System, rocky planets reside close to the Sun while the gas giants orbit at a much greater distance. However, gas giants have previously been discovered orbiting much closer to their star than in our own Solar System, and orbits can move after formation.
This planetary system presents a puzzle as to how two very different worlds ended up in such close orbits.
The two planets orbit their star too closely to be in the "habitable zone" where the temperature is just right for liquid water to exist and thus have the potential for life.
The research team, led by Josh Carter, a Hubble fellow at the Harvard-Smithsonian Center for Astrophysics and Eric Agol, a professor of astronomy at the University of Washington in Seattle, used data from NASA's Kepler space telescope. The findings have been published in the journal Science.
NASA's Kepler telescope was launched in March 2009 and in April 2012 NASA announced that the mission would be extended until 2016.
While Kepler’s main objective is to find potentially habitable terrestrial planets, it can also discover larger planets as these are easier to detect. So far, dozens of gas giants and super-Earths have been found. The planet that is most similar to Earth so far is Kepler-22b, which is 2.4 times the radius of the Earth and orbits a Sun-like star.
Kepler is monitoring more than 150,000 stars to search for dips in light that could indicate the presence of an orbiting planet.
Learn more about NASA's Kepler mission.